This invention is in the field of corn breeding, specifically relating to an inbred corn line designated G2202. This invention also is in the field of hybrid maize production employing the present inbred.
The original maize plant was indigenous to the Western Hemisphere. The plants were weedlike and only through the efforts of early breeders were cultivated crop species developed. The crop cultivated by early breeders, like the crop today, could be wind pollinated. The physical traits of maize are such that wind pollination results in self-pollination or cross-pollination between plants. Each plant has a separate male and female flower that contributes to pollination, the tassel and ear, respectively. Natural pollination occurs when wind transfers pollen from tassel to the silks on the corn ears. This type of pollination has contributed to the wide variation of maize varieties present in the Western Hemisphere.
The development of a planned breeding program for maize only occurred in the last century. A large part of the development of the maize product into a profitable agricultural crop was due to the work done by land grant colleges. Originally, maize was an open pollinated variety having heterogeneous genotypes. The maize farmer selected uniform ears from the yield of these genotypes and preserved them for planting the next season. The result was a field of maize plants that were segregating for a variety of traits. This type of maize selection led to, at most, incremental increases in seed yield.
Large increases in seed yield were due to the work done by land grant colleges that resulted in the development of numerous hybrid corn varieties in planned breeding programs. Hybrids were developed by selecting corn lines and selfing these lines for several generations to develop homozygous pure inbred lines. One selected inbred line was crossed with another selected inbred line to produce hybrid progeny (F1). The resulting hybrids, due to heterosis, are robust and vigorous plants. Inbreds on the other hand are mostly homozygous. This homozygosity renders the inbred lines less vigorous. Inbred seed can be difficult to produce since the inbreeding process in corn lines decreases the vigor. However, when two inbred lines are crossed, the hybrid plant evidences greatly increased vigor and seed yield compared to open pollinated, segregating maize plants. An important consequence of the homozygosity and the homogenity of the inbred maize lines is that all hybrid seed produced from any cross of two such elite lines will be the same hybrid seed and make the same hybrid plant. Thus the use of inbreds makes hybrid seed which can be reproduced readily. The hybrid plant in contrast does not produce hybrid seed that is readily reproducible. The seed on a hybrid plant is segregating for traits.
The ultimate objective of the commercial maize seed companies is to produce high yielding, agronomically sound plants that perform well in certain regions or areas of the Corn Belt. To produce these types of hybrids, the companies must develop inbreds, which carry needed traits into the hybrid combination. Hybrids are not often uniformly adapted for the entire Corn Belt, but most often are specifically adapted for regions of the Corn Belt. Northern regions of the Corn Belt require shorter season hybrids than do southern regions of the Corn Belt. Hybrids that grow well in Colorado and Nebraska soils may not flourish in richer Illinois and Iowa soil. Thus, a variety of major agronomic traits are important in hybrid combination for the various Corn Belt regions, and have an impact on hybrid performance.
Inbred line development and hybrid testing have been emphasized in the past half-century in commercial maize production as a means to increase hybrid performance. Inbred development is usually done by pedigree selection. Pedigree selection can be selection in an F2 population produced from a planned cross of two genotypes (often elite inbred lines), or selection of progeny of synthetic varieties, open pollinated, composite, or backcrossed populations. This type of selection is effective for highly inheritable traits, but other traits, for example, yield requires replicated test crosses at a variety of stages for accurate selection.
Maize breeders select for a variety of traits in inbreds that impact hybrid performance along with selecting for acceptable parental traits. Such traits include: yield potential in hybrid combination; dry down; maturity; grain moisture at harvest; greensnap; resistance to root lodging; resistance to stalk lodging; grain quality; disease and insect resistance; ear and plant height. Additionally, Hybrid performance will differ in different soil types such as low levels of organic matter, clay, sand, black, high pH, low pH; or in different environments such as wet environments, drought environments, and no tillage conditions. These traits appear to be governed by a complex genetic system that makes selection and breeding of an inbred line extremely difficult. Even if an inbred in hybrid combination has excellent yield (a desired characteristic), it may not be useful because it fails to have acceptable parental traits such as seed yield, seed size, pollen production, good silks, plant height, etc.
To illustrate the difficulty of breeding and developing inbred lines, the following example is given. Two inbreds compared for similarity of 29 traits differed significantly for 18 traits between the two lines. If 18 simply inherited single gene traits were polymorphic with gene frequencies of 0.5 in the parental lines, and assuming independent segregation (as would essentially be the case if each trait resided on a different chromosome arm), then the specific combination of these traits as embodied in an inbred would only be expected to become fixed at a rate of one in 262, 144 possible homozygous genetic combinations. Selection of the specific inbred combination is also influenced by the specific selection environment on many of these 18 traits which makes the probability of obtaining this one inbred even more remote. In addition, most traits in the corn genome are regrettably not single dominant genes but are multi-genetic with additive gene action not dominant gene action. Thus, the general procedure of producing a non segregating F1 generation and self pollinating to produce a F2 generation that segregates for traits and selecting progeny with the visual traits desired does not easily lead to a useful inbred. Great care and breeder expertise must be used in selection of breeding material to continue to increase yield and the agronomics of inbreds and resultant commercial hybrids.
Certain regions of the Corn Belt have specific difficulties that other regions may not have. Thus the hybrids developed from the inbreds have to have traits that overcome or at least minimize these regional growing problems. Examples of these problems include in the eastern corn belt Gray Leaf Spot, in the north cool temperatures during seedling emergence, in the Nebraska region CLN (corn Lethal necrosis and in the west soil that has excessively high pH levels. The industry often targets inbreds that address these issues specifically forming niche products. However, the aim of most large seed producers is to provide a number of traits to each inbred so that the corresponding hybrid can useful in broader regions of the Corn Belt. The new biotechnology techniques such as Microsatellites, RFLPs, RAPDs and the like have provided breeders with additional tools to accomplish these goals.
The present invention relates to an inbred corn line G2202. Specifically, this invention relates to plants and seeds of this line. Additionally, this relates to a method of producing from this inbred, hybrid seed corn and hybrid plants with seeds from such hybrid seed. More particularly, this invention relates to the unique combination of traits that combine in corn line G2202.
Generally then, broadly the present invention includes an inbred corn seed designated G2202. This seed produces a corn plant.
The invention also includes the tissue culture of regenerable cells of G2202 wherein the cells of the tissue culture regenerates plants capable of expressing the genotype of G2202. The tissue culture is selected from the group consisting of leaves, pollen, embryos, roots, root tips, guard cells, ovule, seeds, anthers, silk, flowers, kernels, ears, cobs, husks and stalks, cells and protoplasts thereof. The corn plant regenerated from G2202 or any part thereof is included in the present invention. The present invention includes regenerated corn plants that are capable of expressing G2202""s genotype, phenotype or mutants or variants thereof.
The invention extends to hybrid seed produced by planting, in pollinating proximity which includes using preserved maize pollen as explained in U.S. Pat. No. 5,596,838 to Greaves, seeds of corn inbred lines G2202 and another inbred line if preserved pollen is not used; cultivating corn plants resulting from said planting; preventing pollen production by the plants of one of the inbred lines if two are employed; allowing cross pollination to occur between said inbred lines; and harvesting seeds produced on plants of the selected inbred. The hybrid seed produced by hybrid combination of plants of inbred corn seed designated G2202 and plants of another inbred line are apart of the present invention. This inventions scope covers hybrid plants and the plant parts including the grain and pollen grown from this hybrid seed.
The invention further includes a method of hybrid F1 production. A first generation (F1) hybrid corn plant produced by the process of planting seeds of corn inbred line G2202; cultivating corn plants resulting from said planting; permitting pollen from another inbred line to cross pollinate inbred line G2202; harvesting seeds produced on plants of the inbred; and growing a harvested seed are part of the method of this invention.
Likewise included is a first generation (F1) hybrid corn plant produced by the process of planting seeds of corn inbred line G2202; cultivating corn plants resulting from said planting; permitting pollen from inbred line G2202 to cross pollinate another inbred line; harvesting seeds produced on plants of the inbred; and growing a plant from such a harvested seed.
The inbred corn line G2202 and at least one transgenic gene adapted to give G2202 additional and/or altered phenotypic traits are within the scope of the invention. Such transgenes are usually associated with regulatory elements (promoters, enhancers, terminators and the like). Presently, trangenes provide the invention with traits such as insect resistance, herbicide resistance, disease resistance increased or deceased starch or sugars or oils, increased or decreased life cycle or other altered trait.
The present invention includes inbred corn line G2202 and at least one transgenic gene adapted to give G2202 modified starch traits. Furthermore this invention includes the inbred corn line G2202 and at least one mutant gene adapted to give modified starch, acid or oil traits. The present invention includes the inbred corn line G2202 and at least one transgenic gene selected from the group consisting of: bacillus thuringiensis, the bar or pat gene encoding Phosphinothricin acetyl Transferase, Gdha gene, EPSP synthase gene, low phytic acid producing gene, and zein. The inbred corn line G2202 and at least one transgenic gene useful as a selectable marker or a screenable marker are covered by the present invention.
A tissue culture of the regenerable cells of hybrid plants produced with use of G2202 genetic material is covered by this invention. A tissue culture of the regenerable cells of the corn plant produced by the method described above are also included.
In the description and examples, which follow, a number of terms are used. In order to provide a clear and consistent understanding of the specifications and claims including the scope to be given such terms, the following definitions are provided.
BL Moist
The moisture percentage of the grain at black layer, i.e., when 50% of the plants per plot have reached physiological maturity.
Cold Germ
Cold Germ is a measurement of seed germination under cold soil conditions. Data is reported as percent of seed germinating.
ECB
European corn borer is a maize eating insect. ECBI is the first brood generation of European corn borers. ECBII is the second generation of European corn borers. ECB1 is a rating of leaf damage. The ECBII (ECB2) rating is based upon tunneling. For all Entomology ratings, the higher number is best (1=little or no resistance, 9=highly resistant). The scale is slightly different for Ear Rating, which is taken on a 1-4 basis. This is a rating of corn borer feeding on the ear. A 1 represents feeding over the entire ear, while a 4 represents no observable feeding on the ear.
Emerge (EMG)
The number of emerged plants per plot (planted at the same seedling rate) collected when plants have two fully developed leaves.
GI
This is a selection index that provides a single quantitative measure of the worth of a hybrid based on four traits. FI is a very similar index which weights yield less than GI. In GI yield is the primary trait contributing to index values. The GI value is calculated by combining stalk lodging, root lodging, yield and dropped ears according to the attached mathematical formula:
GI=100+0.5(YLD)xe2x88x920.9(% STALK LODGE)xe2x88x920.9(% ROOT LODGE)xe2x88x922.7(% DROPPED EAR)
GLS
Gray Leaf Spot (Cercospora Zeae) disease rating. This is rated on a 1-9 scale with a xe2x80x9c1xe2x80x9d being very susceptible, and a xe2x80x9c9xe2x80x9d being very resistant.*
GW
Gross"" Wilt (Corynebacterium nebraskense). This is rated on a 1-9 scale with a xe2x80x9c1xe2x80x9d being very susceptible, and a xe2x80x9c9xe2x80x9d being very resistant.*
HEATP10
The number of Growing Degree Units (GDU""s) or heat units required for an inbred line or hybrid to have approximately 10 percent of the plants shedding pollen. This trait is measured from the time of planting. Growing Degree Units are calculated by the Barger Method where the GDU""s for a 24 hour period are:   GDU  =                    (                              Max            ⁢                          xe2x80x83                        ⁢                          Temp              ⁡                              (                                                                           xc2x0F                                    .                                )                                              +                      Min            ⁢                          xe2x80x83                        ⁢                          Temp              ⁡                              (                                  xc2x0F                  .                                )                                                    )            2        -    50  
The highest maximum temperature used is 86xc2x0 F. and the lowest minimum temperature used is 50xc2x0 F. For each inbred or hybrid it takes a certain number of GDU""s to reach various stages of plant development.
HEATBL
The number of GDU""s after planting when approximately 50 percent of the inbred or hybrid plants in a plot have grain that has reached physiological maturity (black layer).
Heatpeek
The number of GDU""s after planting of an inbred when approximately 50 percent of the plants show visible tassel extension.
HEATP50 or HTP50
The number of GDU""s required for an inbred or hybrid to have approximately 50 percent of the plants shedding pollen. Growing Degree Units are calculated by the Barger Method as shown in the HEATP10 definition.
HEATP90
The number of GDU""s accumulated from planting when the last 100 percent of plants in an inbred or hybrid are still shedding enough viable pollen for pollination to occur. Growing Degree Units are calculated by the Barger Method as shown in the HEATP10 definition.
HEATS10
The number of GDU""s required for an inbred or hybrid to have approximately 10 percent of the plants with silk emergence of at least 0.5 inches. Growing Degree Units are calculated by the Barger Method as shown in the HEATP10 definition.
HEATS50 or HTS50
The number of GDU""s required for an inbred or hybrid to have approximately 50 percent of the plants with silk emergence of at least 0.5 inches. Growing Degree Units are calculated by the Barger Method as shown in the HEATP10 definition.
HEATS90
The number of GDU""s required for an inbred or hybrid to have approximately 90 percent of the plants with silk emergence of at least 0.5 inches. Growing Degree Units are calculated by the Barger Method as shown in the HEATP10 definition.
MDMVA 
Maize Dwarf Mosaic Virus strain A. The corn is rated on a 1-9 scale with a xe2x80x9c1xe2x80x9d being very susceptible, and a xe2x80x9c9xe2x80x9d being very resistant.*
MDMVB 
Maize Dwarf Mosaic Virus strain B. This is rated on a 1-9 scale with a xe2x80x9c1xe2x80x9d being very susceptible and a xe2x80x9c9xe2x80x9d being very resistant.*
Moisture
The average percentage grain moisture of an inbred or hybrid at harvest time.
NLB
Northern Leaf Blight (Exserohilum turcicum) disease rating. This is rated on a 1-9 scale with a xe2x80x9c1xe2x80x9d being very susceptible, and a xe2x80x9c9xe2x80x9d being very resistant.*
PCT Tiller or Tiller Rating
The total number of tillers per plot divided by the total number of plants per plot.
Plant
This term includes plant cells, plant protoplasts, plant cell tissue cultures from which corn plants can be regenerated, plant calli, plant clumps, and plant cells that are intact in plants or parts of plants, such as embryos, pollen, flowers, kernels, ears, cobs, leaves, husks, stalks, roots, root tips, anthers, silk and the like., and this term also includes any transgenic DNA or (RNA) or portion thereof that have been introduced into the plant by whatever method.
Plant Height (PLTHT) (PHT)
The distance in centimeters from ground level to the base of the tassel peduncle.
Plant Integrity (PLTINT) or (INT)
The level of plant integrity on a scale of 1-9 with 9 evidencing the trait most strongly: 1-2.9 ratings are low plant integrity, 3-5.9 ratings are intermediate plant integrity, and 6-9 ratings are strongly evidencing plant integrity.
Population (POP)
The plant population.
RM
Predicted relative maturity based on the moisture percentage of the grain at harvest. This rating is based on known set of checks and utilizes standard linear regression analyses and is referred to as the Minnesota Relative Maturity Rating System.
Shed
The volume of pollen shed by the male flower rated on a 1-5 scale where a xe2x80x9c1xe2x80x9d is a very light pollen shedder, a xe2x80x9c2.5xe2x80x9d is a moderate shedder, and a xe2x80x9c5xe2x80x9d is a very heavy shedder.
SLB
Southern Leaf Blight (Bipolaris maydis) disease rating. This is rated on a 1-9 scale with a xe2x80x9c1xe2x80x9d being very susceptible, and a xe2x80x9c9xe2x80x9d being very resistant.*
Staygreen (SGN)
The level of staygreen of the plant on a scale of 1-9 with 9 evidencing the trait most strongly: 1-2.9 ratings are low staygreen, 3-5.9 ratings are intermediate staygreen, and 6-9 ratings are strongly evidencing staygreen.
TWT
The measure of the weight of grain in pounds for a one bushel volume adjusted for percent grain moisture.
Vigor (VIG)
Visual rating of 1 to 9 made 2-3 weeks post-emergence where a xe2x80x9c1xe2x80x9d indicates very poor early plant development, and a xe2x80x9c9xe2x80x9d indicates superior plant development.
Warm Germ
A measurement of seed germination under ideal (warm, moist) conditions. Data is reported as percent of seeds germinating.
Yield (YLD)
Actual yield of grain at harvest adjusted to 15.5% moisture. Measurements are reported in bushels per acre.
% Dropped Ears (DE)
The number of plants per plot, which dropped their primary ear, divided by the total number of plants per plot.
% Root Lodge (RL)
Percentage of plants per plot leaning more that 30 degrees from vertical divided by total plants per plot.
% Stalk Lodge (SL)
Percentage of plants per plot with the stalk broken below the primary ear node divided by the total plants per plot.
Resistantxe2x80x94on a scale of 1-9 with 9 evidencing the trait most strongly: 1-2.9 ratings are susceptible, 3-5.9 ratings are intermediate, and 6-9 ratings are resistant.